Add regression test for HINCRBYFLOAT formatting change.
Add regression test for HINCRBYFLOAT formatting change.

This test was kindly provided by Jan-Erik Rediger (@badboy here on
Github) that discovered the issue.

See issue #2846.

JackieXie168/redis,JackieXie168/redis,JackieXie168/redis,JackieXie168/redis